Something Harmless; Something Harmful

Something harmless; something harmful in the garden

By Ralph E. Mitchell

Our customers are often a great barometer of what is going on in the gardening world of Charlotte County. They bring us specimens to identify and describe conditions that they see happening in their landscapes. Sometimes the things that they see are visually disturbing, but turn out to be totally harmless. Other times, however, there are genuine problem pests at work that need to be dealt with immediately. Take the cases of the webbing barklouse and the larger canna leafroller - two unrelated, yet current insects at work in the area.

The webbing barklouse is first of all not a true louse, but does resemble one. They are closely related to the booklouse which tends to inhabit places where books are stored indoors. Webbing barklice are very small, flattened insects with or without wings. The main visual clue that tells you that they are around is a large silken web that covers trunks and branches of trees. At first glance, it may appear to be the work of a spider or even an early decoration for Halloween! Colonies of these barklice spin these webs to cover their insect community. From July to October these webs appear and are believed to actually protect these insects from predators. Barklice are then able to feed on lichen (a harmless fungi/algal organism) safely under this tent of webbing. Eventually by December, time and the weather break down the webbing about the same time the barklice populations are killed by frosts. Although the appearance of the webs may bring alarm to some people, these insects are completely harmless and no control action is needed nor recommended.

A different scenario involves seeing your cannas suddenly looking ragged and heavily chewed. Upon closer inspection, you see some of the remaining leaves rolled up into tubes. Each of these tubes harbors a large green caterpillar up to fifty-five millimeters in length known as the larger canna leafroller. The caterpillar can emerge from this self- made shelter to feed and then retreat for safety. The tubes are made when the caterpillar manipulates the leaf via chewing and attaching stands of silk. The larger canna leafroller actually flicks its tell-tale droppings away from its tubular home to get predators, parasites and curious gardeners off their trail. The feeding damage caused by these caterpillars may be so severe that the cannas flowers are affected. The beauty of the ornamental leaves is also ruined. While some studies have suggested that the larger canna leafroller tends to home-in on red-leaved varieties and those with scarlet, red or orange flowers, no cannas are resistant to this pest. Natural predators, parasites, and disease show up in these caterpillars, but they don't reduce the population enough. Probably the best control option is the use of products which contain Bacillus thuringiensis or Bt. This product comes under a number of different brand names, but as always read the label as the label is the law. Keep in mind that Bt is most effective with small caterpillars. A sticker, added to help the insecticide better adhere to the waxy- leaved cannas, is also recommended. While some appearances can be deceiving, others are right on and action must be taken. Always identify the pest problem first before you take action - we can help you! For more information on all types of insects, both good and bad, please contact our Master Gardeners on the Plant Lifeline at 764-4340 from 1 p.m. to 4 p.m. Mondays, Wednesdays and Fridays. Our office is located at 25550 Harbor View Road, Suite 3 in Port Charlotte. Our other Plant Clinics are available across the county: Demonstration Garden every Thursday from 9 to 11 a.m. Englewood/Charlotte Public Library 9 a.m. to noon every Monday. Mid County Regional Library first and third Thursday of the month from 1 to 3 p.m. Monthly Plant Clinics are Saturdays from 9 a.m. to noon at the following locations: Cape Haze Publix first Saturday of the month; Peachland Promenades Publix ‹ second Saturday of the month; Home Depot Murdock and Home Depot Punta Gorda the third Saturday of the month

Don't forget that Florida Yards and Neighborhoods or FYN is a program that our office encourages as it promotes planting the "right plant in the right place", water conservation, common sense pest management, sensible use of fertilizers, composting, etc. that help develop a sustainable landscape. For more information on this important, over-arching program, please contact Audrey Durr at 764-4340. Ralph Mitchell is the county extension director/horticulture agent for the Charlotte County Cooperative Extension Service. You may contact him by e-mail [email protected] You may also contact a volunteer Master Gardener at [email protected]

Resources:

Hall, D. W. & Butler, J. F. (2002) Webbing Barklouse, a Psocid, Featured Creatures. The University of Florida Extension Service, IFAS.

Koehler, P. G., Branscome, D., and Oi, F. M. (2003) Booklice and Silverfish. The University of Florida Extension Service, IFAS.

McAuslane, H. J. & King, K. (2004) Larger Canna Leafroller, Featured Creatures. The University of Florida Extension Service, IFAS.